U.S. patent application number 14/584099 was filed with the patent office on 2015-04-30 for selective titanium nitride etching.
The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Zhijun Chen, Ching-Mei Hsu, Nitin K. Ingle, Jie Liu, Seung Park, Anchuan Wang, Jingchun Zhang.
Application Number | 20150118857 14/584099 |
Document ID | / |
Family ID | 50975111 |
Filed Date | 2015-04-30 |
United States Patent
Application |
20150118857 |
Kind Code |
A1 |
Liu; Jie ; et al. |
April 30, 2015 |
SELECTIVE TITANIUM NITRIDE ETCHING
Abstract
Methods of etching exposed titanium nitride with respect to
other materials on patterned heterogeneous structures are
described, and may include a remote plasma etch formed from a
fluorine-containing precursor. Precursor combinations including
plasma effluents from the remote plasma are flowed into a substrate
processing region to etch the patterned structures with high
titanium nitride selectivity under a variety of operating
conditions. The methods may be used to remove titanium nitride at
faster rates than a variety of metal, nitride, and oxide
compounds.
Inventors: |
Liu; Jie; (Sunnyvale,
CA) ; Zhang; Jingchun; (Cupertino, CA) ; Wang;
Anchuan; (San Jose, CA) ; Ingle; Nitin K.;
(San Jose, CA) ; Park; Seung; (San Jose, CA)
; Chen; Zhijun; (San Jose, CA) ; Hsu;
Ching-Mei; (Stanford, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
50975111 |
Appl. No.: |
14/584099 |
Filed: |
December 29, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13791125 |
Mar 8, 2013 |
8921234 |
|
|
14584099 |
|
|
|
|
61740587 |
Dec 21, 2012 |
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Current U.S.
Class: |
438/715 ;
438/710 |
Current CPC
Class: |
H01J 37/32357 20130101;
H01L 21/32136 20130101 |
Class at
Publication: |
438/715 ;
438/710 |
International
Class: |
H01L 21/3213 20060101
H01L021/3213 |
Claims
1. A method of etching a patterned substrate in a substrate
processing region of a substrate processing chamber, wherein the
patterned substrate includes an exposed titanium nitride region and
a region comprising an exposed second material, the method
comprising: flowing a fluorine-containing precursor into a remote
plasma region fluidly coupled with the substrate processing region
while forming a plasma in the remote plasma region to produce
plasma effluents; flowing the plasma effluents through a showerhead
positioned between the remote plasma region and the substrate
processing region; flowing at least one additional precursor into
the substrate processing region; and etching the exposed titanium
nitride region with the precursor combination including the plasma
effluents, wherein the titanium nitride is etched at a faster rate
than the exposed second material.
2. The method of claim 1, wherein the at least one additional
precursor is selected from the group consisting of helium, argon,
and molecular hydrogen (H.sub.2).
3. The method of claim 1, wherein the fluorine-containing precursor
comprises a precursor selected from the group consisting of atomic
fluorine, diatomic fluorine, nitrogen trifluoride, carbon
tetrafluoride, hydrogen fluoride, and xenon difluoride.
4. The method of claim 1, wherein the plasma in the remote plasma
region is a capacitively-coupled plasma.
5. The method of claim 1, wherein the substrate processing region
is plasma-free during the etching process.
6. The method of claim 1, wherein the at least one additional
precursor consists of either or both of helium and argon.
7. The method of claim 6, wherein the precursor combination
including plasma effluents is substantially devoid of hydrogen.
8. The method of claim 6, wherein the exposed second material
comprises silicon oxide and the selectivity of the etching
operation (exposed titanium nitride region:exposed silicon oxide
region) is greater than or about 5:1.
9. (canceled)
10. The method of claim 6, wherein the substrate temperature is
maintained at or below about 50.degree. C. during the etch
process.
11. The method of claim 10, wherein the substrate temperature is
maintained at or below about 10.degree. C. during the etch
process.
12. The method of claim 1, wherein the at least one additional
precursor comprises hydrogen.
13. The method of claim 12, wherein the exposed second material
comprises tungsten and the selectivity of the etching operation
(exposed titanium nitride region:exposed tungsten region) is
greater than or about 50:1.
14. The method of claim 13, wherein the selectivity of the etching
operation (exposed titanium nitride region:exposed tungsten region)
is greater than or about 100:1.
15. The method of claim 13, wherein the patterned substrate further
comprises an exposed silicon nitride region and the selectivity of
the etching operation (exposed titanium nitride region:exposed
silicon nitride region) is greater than or about 10:1.
16. The method of claim 13, wherein the patterned substrate further
comprises an exposed silicon oxide region and the selectivity of
the etching operation (exposed titanium nitride region:exposed
silicon oxide region) is greater than or about 5:1.
17. The method of claim 13, wherein the patterned substrate further
comprises an exposed tantalum nitride region and the selectivity of
the etching operation (exposed titanium nitride region:exposed
tantalum nitride region) is greater than or about 10:1.
18. The method of claim 12, wherein the substrate temperature is
maintained at or above about 50.degree. C. during the etch
process.
19. The method of claim 18, wherein the substrate temperature is
maintained at or above about 200.degree. C. during the etch
process.
20. The method of claim 12, wherein the hydrogen is flowed into the
substrate processing region without being first excited in a remote
plasma.
21. A method of etching a patterned substrate in a substrate
processing region of a substrate processing chamber, wherein the
patterned substrate includes an exposed titanium nitride region and
a region comprising an exposed second material, the method
comprising: flowing a fluorine-containing precursor into a remote
plasma region fluidly coupled with the substrate processing region
while forming a plasma in the remote plasma region to produce
plasma effluents; flowing the plasma effluents through a showerhead
positioned between the remote plasma region and the substrate
processing region; flowing molecular hydrogen (H.sub.2) into the
substrate processing region; and etching the exposed titanium
nitride region with the precursor combination including the plasma
effluents, wherein the titanium nitride is etched at a faster rate
than the exposed second material.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/791,125, filed Mar. 8, 2013, entitled
"Selective Titanium Nitride Etching" which claims the benefit of
U.S. Provisional Application No. 61/740,587, filed Dec. 21, 2012,
entitled "Selective Titanium Nitride Etching." The entire
disclosure of which is incorporated herein by reference for all
purposes.
TECHNICAL FIELD
[0002] The present technology relates to semiconductor processes
and equipment. More specifically, the present technology relates to
selective etching of materials on semiconductor substrates.
BACKGROUND
[0003] Integrated circuits are made possible by processes which
produce intricately patterned material layers on substrate
surfaces. Producing patterned material on a substrate requires
controlled methods for removal of exposed material. Chemical
etching is used for a variety of purposes including transferring a
pattern in photoresist into underlying layers, thinning layers, or
thinning lateral dimensions of features already present on the
surface. Often it is desirable to have an etch process that etches
one material faster than another facilitating, for example, a
pattern transfer process. Such an etch process is said to be
selective to the first material. As a result of the diversity of
materials, circuits, and processes, etch processes have been
developed with a selectivity towards a variety of materials.
[0004] A wet HF etch preferentially removes silicon oxide over
other dielectrics and semiconductors. However, wet processes are
unable to penetrate some constrained trenches and sometimes deform
the remaining material. Dry etches produced in local plasmas formed
within the substrate processing region can penetrate more
constrained trenches and exhibit less deformation of delicate
remaining structures. However, local plasmas can damage the
substrate through the production of electric arcs as they
discharge.
[0005] Thus, there is a need for improved methods and systems for
selectively etching materials and structures on semiconductor
substrates. These and other needs are addressed by the present
technology.
SUMMARY
[0006] Methods of etching exposed titanium nitride with respect to
other materials on patterned heterogeneous structures are
described, and may include a remote plasma etch formed from a
fluorine-containing precursor. Precursor combinations including
plasma effluents from the remote plasma are flowed into a substrate
processing region to etch the patterned structures with high
titanium nitride selectivity under a variety of operating
conditions. The methods may be used to remove titanium nitride at
faster rates than a variety of metal, nitride, and oxide
compounds.
[0007] The at least one additional precursor may include one or
more precursors selected from the group consisting of helium,
argon, and molecular hydrogen (H.sub.2). The fluorine-containing
precursor may include one or more precursors selected from the
group consisting of atomic fluorine, diatomic fluorine, nitrogen
trifluoride, carbon tetrafluoride, hydrogen fluoride, and xenon
difluoride. The methods may be performed such that the processing
region in which the semiconductor substrate resides is plasma-free
during the etching process.
[0008] The methods may include having the additional precursor
consist of one or both of helium and argon. The precursor
combination delivered into the processing region may be
substantially devoid of hydrogen. The exposed second material may
include silicon oxide and/or silicon nitride, and the selectivity
of the etching operation (exposed titanium nitride region:exposed
silicon oxide region) may be greater than or about 5:1, and in
disclosed embodiments may be greater than or about 10:1. The
substrate temperature may be maintained below or about 50.degree.
C. during the etch process, and in disclosed embodiments may be
maintained at or below about 10.degree. C. during the etch
process.
[0009] The methods can include that the at least one additional
precursor comprises hydrogen, and may additionally include one or
more carrier gases including helium or argon. The exposed second
material may include tungsten, and the selectivity of the etching
operation (exposed titanium nitride region:exposed tungsten region)
may be greater than or about 50:1, and in disclosed embodiments may
be greater than or about 100:1. The patterned substrate may further
include additional exposed regions or materials, and in disclosed
embodiments the substrate further comprises an exposed silicon
nitride region. The selectivity of the etching operation (exposed
titanium nitride region:exposed silicon nitride region) may be
greater than or about 10:1. The patterned substrate may further
include an exposed silicon oxide region, and the selectivity of the
etching operation (exposed titanium nitride region:exposed silicon
oxide region) may be greater than or about 5:1. The patterned
substrate may further include an exposed tantalum nitride region,
and the selectivity of the etching operation (exposed titanium
nitride region:exposed tantalum nitride region) may be greater than
or about 10:1. The substrate temperature may be maintained at or
above about 50.degree. C. during the etch process, and in disclosed
embodiments may be maintained at or above about 200.degree. C.
during the etch process. The method may include flowing the
hydrogen into the substrate processing region without its being
excited by any remote plasma prior to entering the processing
region. The plasma utilized in the methods in the remote plasma
region may be a capacitively-coupled plasma.
[0010] Such technology may provide numerous benefits over
conventional techniques. For example, process throughput may be
increased based on the improved selectivity. Additionally, less
protection of exposed materials may be required with the improved
selective etching with respect to multiple materials. These and
other embodiments, along with many of their advantages and
features, are described in more detail in conjunction with the
below description and attached figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A further understanding of the nature and advantages of the
disclosed technology may be realized by reference to the remaining
portions of the specification and the drawings.
[0012] FIG. 1 shows a flow chart of a titanium nitride selective
etch process according to disclosed embodiments.
[0013] FIG. 2A shows a schematic cross-sectional view of a
substrate processing chamber according to the disclosed
technology.
[0014] FIG. 2B shows a schematic cross-sectional view of a portion
of a substrate processing chamber according to the disclosed
technology.
[0015] FIG. 2C shows a bottom plan view of a showerhead according
to the disclosed technology.
[0016] FIG. 3 shows a top plan view of an exemplary substrate
processing system according to the disclosed technology.
[0017] In the appended figures, similar components and/or features
may have the same numerical reference label. Further, various
components of the same type may be distinguished by following the
reference label by a letter that distinguishes among the similar
components and/or features. If only the first numerical reference
label is used in the specification, the description is applicable
to any one of the similar components and/or features having the
same first numerical reference label irrespective of the letter
suffix.
DETAILED DESCRIPTION
[0018] The present technology includes improved processes and
chemistry profiles for removing titanium nitride on patterned
semiconductor substrates with respect to other materials. While
conventional processes may remove titanium nitride at slower or
equal rates than other materials, the presently described
technology allows for improved rates of titanium nitride removal.
In so doing, substrate throughput may be improved in a variety of
ways. For example, the rate at which compositions are etched may be
increased. Additionally, less material may be required as initially
deposited or located in, on, or as part of the patterned substrate
with respect to the titanium nitride to be removed. If additional
material located on the substrate with titanium nitride is to be
maintained, but etches at the same rate as titanium nitride, for
example, additional material would generally need to be initially
deposited or located beyond what is to be maintained that is
proportional to the etch rate with respect to the amount of
titanium nitride to be removed. Accordingly, process times may
increase. However, if the selectivity to titanium nitride can be
increased, less of the second material will be removed, and less
additional material would need to have been initially deposited or
located on the substrate. Accordingly, process times can be
reduced.
[0019] Methods of etching exposed titanium nitride with respect to
other materials on patterned heterogeneous structures are
described, and may include a remote plasma etch formed from a
fluorine-containing precursor. Precursor combinations including
plasma effluents from the remote plasma are flowed into a substrate
processing region to etch the patterned structures with high
titanium nitride selectivity under a variety of operating
conditions. The methods may be used to remove titanium nitride at
faster rates than a variety of metal, nitride, and oxide
compounds.
[0020] Selective dry etch processes may be used to remove one
material with respect to another material on patterned
semiconductor substrates. However, depending on the exposed
materials, process gases and process conditions may not provide
adequate etch rates of one material without damaging exposed
features of another material. The presence of certain precursor
chemicals may directly affect the etch rates and selectivities of a
variety of materials. The inventors have advantageously determined
that the selectivity of titanium nitride over a variety of
materials can be enhanced by exciting a fluorine-containing
precursor in a remote plasma, and limiting the additional
precursors that are used in conjunction with the
fluorine-containing precursor based on the material that is to be
maintained.
[0021] In order to better understand and appreciate the invention,
reference is now made to FIG. 1, which shows a flow chart of a
titanium nitride selective etch process according to disclosed
embodiments. Prior to the first operation, the substrate may be
patterned leaving exposed regions of titanium nitride and exposed
regions of a second material that may include one or more of
tantalum nitride, tungsten, silicon nitride, silicon oxide, etc.
Various front end processing may have been performed including the
formation of gates, vias, and other structures. The patterned
substrate may then be delivered to a substrate processing region at
operation 110. In disclosed embodiments, the substrate may already
be located in the processing region if a previous operation was
performed in the same chamber in which the etch process is to
occur. Nitrogen trifluoride (NF.sub.3) may be flowed into a plasma
region that is separate from, but fluidly coupled with, the
processing region at operation 120. Other sources of fluorine may
be used in conjunction with or as replacements for the nitrogen
trifluoride. In general, a fluorine-containing precursor is flowed
into the plasma region and the fluorine-containing precursor
comprises at least one precursor selected from the group consisting
of atomic fluorine, diatomic fluorine, nitrogen trifluoride, carbon
tetrafluoride, hydrogen fluoride, and xenon difluoride.
[0022] The separate plasma region may be referred to as a remote
plasma region herein and may be within a distinct module from the
processing chamber, or as a compartment within the processing
chamber. A plasma may be formed within the remote plasma region
thereby generating plasma effluents from the fluorine-containing
precursor. At operation 130, one or more additional precursors may
be flowed that are either additionally flowed into the plasma
region, or directed to bypass the plasma region to flow unexcited
into the processing region. The additional precursors may include
carrier gases, such as for example helium or argon, and may
additionally include a hydrogen source, including molecular
hydrogen (H.sub.2) in disclosed embodiments. The combination of
precursors including the plasma effluents is directed to flow into
the processing region at operation 140. As previously stated, the
precursors may have been pre-mixed in the remote plasma region, or
the precursors may be fluidly isolated from one another until they
are separately delivered into the processing region.
[0023] The patterned substrate may be selectively etched with the
precursor combination including plasma effluents at operation 150,
such that the exposed titanium nitride region is removed at a
higher rate than the exposed second material on the patterned
substrate. The reactive chemical species may be removed from the
substrate processing region, and then the substrate may be removed
from the processing region at operation 160. Using the gas phase
dry etch processes described herein, the inventors have established
that etch selectivities of over 5:1 with regard to the titanium
nitride etch rate as compared to the etch rate of other materials
are possible. Achievable selectivities using the methods described
herein are additionally capable of etching titanium nitride at
rates faster than a second material that typically etches faster
than titanium nitride, such as tungsten, as will be described in
greater detail below. The titanium nitride etch rate may exceed the
exposed second material etch rate by a multiplicative factor of up
to or about 5 or more, about 10 or more, about 15 or more, about 20
or more, about 50 or more, about 75 or more, about 100 or more,
etc. or greater in embodiments of the technology.
[0024] Depending on the additional precursor or precursors used in
the exemplary processes, the rates of titanium nitride etching with
respect to the exposed second material may by affected. For
example, in disclosed embodiments the additional precursor may be
one or more precursors selected from the group consisting of
helium, argon, and molecular hydrogen (H.sub.2). In other
embodiments, other hydrogen-containing precursors may be used
including ammonia, for example. Depending on what additional
materials are exposed, these gases may be used in combination to
adjust etch characteristics.
[0025] When the exposed materials include titanium nitride and
certain other materials including silicon nitride or silicon oxide,
the one or more additional precursors may include only carrier
gases, such as helium and/or argon. In one embodiment, the
additional precursors consist exclusively of helium and/or argon.
Put another way, the precursor combination including plasma
effluents delivered to the processing region may be completely or
substantially devoid of any hydrogen or hydrogen-containing
precursors. The additional precursors may be flowed with the
fluorine-containing precursor into the plasma region to produce
plasma effluents. When these precursor combinations including
plasma effluents are delivered into the processing region, the
selectivity of the etching operation of an exposed titanium nitride
region to an exposed silicon oxide region may be up to, greater
than, or about 2:1. The etching selectivity may also be up to,
greater than, or about 5:1, 10:1, 15:1, 17:1, 20:1, etc. or more.
In terms of material etched, in one minute of processing time about
100 Angstrom or more of titanium nitride may be etched while less
than or about 20 Angstrom of silicon oxide may be removed. In other
embodiments less than or about 15 Angstrom, 12, 10, 9, 8, 7, 6, 5,
4, 3, 2, 1, or 0 Angstrom of silicon oxide may be removed, the last
case indicating that the silicon oxide is maintained during the
etching of titanium nitride.
[0026] During the etching process, the substrate may be maintained
at or below about 400.degree. C., and may be maintained at or below
about 300.degree. C., 200.degree. C., 100.degree. C., 80.degree.
C., 75.degree. C., 50.degree. C., 25.degree. C., 10.degree. C.,
0.degree. C., or less. The processing chamber may be maintained at
or below about 100 Torr during the processes, and may be maintained
at or below about 50 Torr, 25 Torr, 15 Torr, 5 Torr, 1 Torr, 0.1
Torr, etc., or between about 0.1 mTorr and about 10 Torr. By
maintaining the substrate temperature at lower temperatures, such
as about 10.degree. C. or less, and maintaining the process chamber
at a pressure below about 10 Torr, the inventors have determined
that the amount of oxide removal can be further limited during the
removal of titanium nitride.
[0027] Certain materials may typically etch at a faster rate than
titanium nitride, including other metals such as tungsten. For
example, if the above-described etch process is performed, any
exposed tungsten may etch faster than the exposed titanium nitride.
If a region of titanium nitride is to be removed, but an exposed
region of tungsten is to be maintained, these etching processes may
be difficult to control and may damage the tungsten features. To
address the selectivity of tungsten to titanium nitride, the
inventors have determined that by including hydrogen as one of the
additional precursors, the rate at which tungsten etches may be
slowed significantly such that the selectivity to titanium nitride
reverses, and in disclosed embodiments the rate at which tungsten
is etched can be reduced to about zero.
[0028] In embodiments, the precursors may include molecular
hydrogen with the fluorine-containing radical, or alternatively a
hydrogen-containing precursor. The hydrogen may be included with
the fluorine-containing radical and carrier gas or gases discussed
above that are delivered into the remote plasma region where the
plasma effluents are developed. Alternatively, the hydrogen may be
delivered separately from the fluorine-containing precursor such
that it bypasses the remote plasma region. For example, when a
dual-channel showerhead such as that discussed below is utilized,
the hydrogen may be delivered into the volume defined by the
showerhead plates. Accordingly, the hydrogen may be delivered to
the processing region without being excited by any remote plasma,
and it may not come into contact with the plasma effluents until it
enters the processing region.
[0029] When these precursor combinations including hydrogen and
containing plasma effluents are delivered into the processing
region, the selectivity of the etching operation of an exposed
titanium nitride region to an exposed tungsten region may be up to,
greater than, or about 10:1. The etching selectivity may also be up
to, greater than, or about 20:1, 50:1, 100:1, 500:1, 1000:1, etc.
or more, up to the point at which the process is fully selective to
titanium nitride and no tungsten is removed. In terms of material
etched, in one minute of processing time up to or about 3 Angstrom
or more, 6 Angstrom or more, or 10 Angstrom or more of titanium
nitride may be etched while less than or about 1 Angstrom of
tungsten may be removed. In other embodiments less than or about
0.5 Angstrom, 0.1, 0.05, 0.01, 0.005, 0.001, 0.0001, or 0 Angstrom
of tungsten may be removed, that last case of which indicates that
the exposed tungsten region is completely maintained.
[0030] This process may additionally remove titanium nitride with
respect to other materials as well. For example, when titanium
nitride is used in gate applications as an interface layer, or as a
hard mask for patterning low-k stacks, additionally exposed
materials may include one or more materials such as metals
including tungsten, and materials including silicon nitride,
silicon oxide, and tantalum nitride. In many applications, these
layers are to be maintained as much as possible during the titanium
nitride removal. Utilizing the processes encompassed by this
technology, titanium nitride may be etched with respect to all of
these materials, and the selectivity to titanium nitride with
respect to each material may be at least or about 5:1. In disclosed
embodiments, titanium nitride may be etched with respect to silicon
oxide, and the selectivity of the etching operation may be greater
than or about 2:1, or greater than or about 5:1. Titanium nitride
may be etched with respect to silicon nitride, and the selectivity
of the etching operation may be greater than or about 5:1, or
greater than or about 10:1. Titanium nitride may also be etched
with respect to tantalum nitride, and the selectivity of the
etching operation may be greater than or about 5:1, or greater than
or about 10:1.
[0031] By utilizing the hydrogen precursor, the plasma density with
respect to the fluorine-containing precursor may be reduced, which
may reduce the etch rate of the materials. This in turn may reduce
the substrate throughput for these processes. Etch rate may often
be increased by increasing the substrate temperature, but this may
also increase the rate at which materials to be maintained are
etched. However, the inventors have determined that the process
chemistries utilizing hydrogen described in this technology may act
synergistically when the temperatures are raised, such that the
rate at which titanium nitride is removed may increase faster than
the etch rate of other materials to be maintained. Accordingly, the
processes may allow the substrate to be maintained at or above
about 0.degree. C. or between about 0.degree. C. and about
400.degree. C., but may also be maintained at or above about
10.degree. C., 25.degree. C., 50.degree. C., 75.degree. C.,
80.degree. C., 100.degree. C., 200.degree. C., 300.degree. C.,
400.degree. C., or more. The processing chamber may be maintained
at or below about 100 Torr, and may be maintained at or below about
50 Torr, 25 Torr, 15 Torr, 5 Torr, 1 Torr, 0.1 Torr, etc., or
between about 0.1 mTorr and about 10 Torr.
[0032] The described processes may also be used in conjunction with
one another for a variety of operations in which tungsten and
titanium nitride may be both located and exposed on patterned
substrates. For example, in gate structures including NAND or 3D
NAND devices, both tungsten and titanium nitride may be located on
the substrate as gate metal and barrier material respectively.
During processing, the exposed gate metal may need to be recessed
while maintaining a portion of titanium nitride, or otherwise
etching the titanium nitride at a slower rate. Accordingly, the
described chemistry devoid of hydrogen may be utilized at a lower
substrate temperature, which may remove tungsten at a rate faster
than titanium nitride.
[0033] The recessing operation may expose regions or additional
regions of titanium nitride, and may additionally expose regions of
tantalum nitride, silicon nitride, and silicon oxide, for example.
Once the tungsten has been recessed but otherwise maintained,
further etching of the titanium nitride and or other exposed
materials may be needed without further etching, or with minimal
further etching, of the remaining tungsten. Accordingly, the
described process synergistically utilizing hydrogen as a precursor
with increased temperature may be performed. For example, the
substrate temperature may be increased while hydrogen is
incorporated with the precursor fluids. Consequently, further
etching of the tungsten may be minimized while exposed titanium
nitride may be removed. In this way, by combining these etching
processes, etching of titanium nitride with respect to tungsten may
be modified tuned in situ. By utilizing the combined processes,
tungsten may be etched faster than titanium nitride, titanium
nitride may be etched faster than tungsten, or the two materials
may be etched at substantially similar or directly equivalent rates
by adjusting the hydrogen concentration and/or certain of the
processing conditions such as temperature. As would be understood,
additional modifications to chamber pressure and plasma power may
be used to further tune the etching processes as may be required.
Advantageously, tuning these processes may be performed without the
need to break vacuum conditions or move the substrate to an
additional chamber. This may reduce overall processing times and
save costs over conventional techniques. Additional examples of
etch process parameters, chemistries, and components are disclosed
in the course of describing an exemplary processing chamber and
system below.
Exemplary Processing System
[0034] FIG. 2A shows a cross-sectional view of an exemplary process
chamber section 200 with partitioned plasma generation regions
within the processing chamber. During film etching, e.g., titanium
nitride, tantalum nitride, tungsten, silicon, polysilicon, silicon
oxide, silicon nitride, silicon oxynitride, silicon oxycarbide,
etc., a process gas may be flowed into the first plasma region 215
through a gas inlet assembly 205. A remote plasma system (RPS) 201
may optionally be included in the system, and may process a first
gas which then travels through gas inlet assembly 205. The inlet
assembly 205 may include two or more distinct gas supply channels
where the second channel (not shown) may bypass the RPS 201, if
included. Accordingly, in disclosed embodiments the precursor gases
may be delivered to the processing chamber in an unexcited state.
In another example, the first channel provided through the RPS may
be used for the process gas and the second channel bypassing the
RPS may be used for a treatment gas in disclosed embodiments. The
process gas may be excited within the RPS 201 prior to entering the
first plasma region 215. Accordingly, the fluorine-containing
precursor as discussed above, for example, may pass through RPS 201
or bypass the RPS unit in disclosed embodiments. Various other
examples encompassed by this arrangement will be similarly
understood.
[0035] A cooling plate 203, faceplate 217, ion suppressor 223,
showerhead 225, and a substrate support 265, having a substrate 255
disposed thereon, are shown and may each be included according to
disclosed embodiments. The pedestal 265 may have a heat exchange
channel through which a heat exchange fluid flows to control the
temperature of the substrate. This configuration may allow the
substrate 255 temperature to be cooled or heated to maintain
relatively low temperatures, such as between about -20.degree. C.
to about 200.degree. C., or therebetween. The heat exchange fluid
may comprise ethylene glycol and/or water. The wafer support
platter of the pedestal 265, which may comprise aluminum, ceramic,
or a combination thereof, may also be resistively heated in order
to achieve relatively high temperatures, such as from up to or
about 100.degree. C. to above or about 1100.degree. C., using an
embedded resistive heater element. The heating element may be
formed within the pedestal as one or more loops, and an outer
portion of the heater element may run adjacent to a perimeter of
the support platter, while an inner portion runs on the path of a
concentric circle having a smaller radius. The wiring to the heater
element may pass through the stem of the pedestal 265, which may be
further configured to rotate.
[0036] The faceplate 217 may be pyramidal, conical, or of another
similar structure with a narrow top portion expanding to a wide
bottom portion. The faceplate 217 may additionally be flat as shown
and include a plurality of through-channels used to distribute
process gases. Plasma generating gases and/or plasma excited
species, depending on use of the RPS 201, may pass through a
plurality of holes, shown in FIG. 2B, in faceplate 217 for a more
uniform delivery into the first plasma region 215.
[0037] Exemplary configurations may include having the gas inlet
assembly 205 open into a gas supply region 258 partitioned from the
first plasma region 215 by faceplate 217 so that the gases/species
flow through the holes in the faceplate 217 into the first plasma
region 215. Structural and operational features may be selected to
prevent significant backflow of plasma from the first plasma region
215 back into the supply region 258, gas inlet assembly 205, and
fluid supply system 210. The structural features may include the
selection of dimensions and cross-sectional geometries of the
apertures in faceplate 217 to deactivate back-streaming plasma. The
operational features may include maintaining a pressure difference
between the gas supply region 258 and first plasma region 215 that
maintains a unidirectional flow of plasma through the showerhead
225. The faceplate 217, or a conductive top portion of the chamber,
and showerhead 225 are shown with an insulating ring 220 located
between the features, which allows an AC potential to be applied to
the faceplate 217 relative to showerhead 225 and/or ion suppressor
223. The insulating ring 220 may be positioned between the
faceplate 217 and the showerhead 225 and/or ion suppressor 223
enabling a capacitively coupled plasma (CCP) to be formed in the
first plasma region. A baffle (not shown) may additionally be
located in the first plasma region 215, or otherwise coupled with
gas inlet assembly 205, to affect the flow of fluid into the region
through gas inlet assembly 205.
[0038] The ion suppressor 223 may comprise a plate or other
geometry that defines a plurality of apertures throughout the
structure that are configured to suppress the migration of
ionically-charged species out of the plasma excitation region 215
while allowing uncharged neutral or radical species to pass through
the ion suppressor 223 into an activated gas delivery region
between the suppressor and the showerhead. In disclosed
embodiments, the ion suppressor 223 may comprise a perforated plate
with a variety of aperture configurations. These uncharged species
may include highly reactive species that are transported with less
reactive carrier gas through the apertures. As noted above, the
migration of ionic species through the holes may be reduced, and in
some instances completely suppressed. Controlling the amount of
ionic species passing through the ion suppressor 223 may provide
increased control over the gas mixture brought into contact with
the underlying wafer substrate, which in turn may increase control
of the deposition and/or etch characteristics of the gas mixture.
For example, adjustments in the ion concentration of the gas
mixture can significantly alter its etch selectivity, e.g.,
TiNx:SiOx etch ratios, TiN:W etch ratios, etc. In alternative
embodiments in which deposition is performed, it can also shift the
balance of conformal-to-flowable style depositions for dielectric
materials.
[0039] The plurality of holes in the ion suppressor 223 may be
configured to control the passage of the activated gas, i.e., the
ionic, radical, and/or neutral species, through the ion suppressor
223. For example, the aspect ratio of the holes, or the hole
diameter to length, and/or the geometry of the holes may be
controlled so that the flow of ionically-charged species in the
activated gas passing through the ion suppressor 223 is reduced.
The holes in the ion suppressor 223 may include a tapered portion
that faces the plasma excitation region 215, and a cylindrical
portion that faces the showerhead 225. The cylindrical portion may
be shaped and dimensioned to control the flow of ionic species
passing to the showerhead 225. An adjustable electrical bias may
also be applied to the ion suppressor 223 as an additional means to
control the flow of ionic species through the suppressor.
[0040] The ion suppression element 223 may function to reduce or
eliminate the amount of ionically charged species traveling from
the plasma generation region to the substrate. Uncharged neutral
and radical species may still pass through the openings in the ion
suppressor to react with the substrate. It should be noted that the
complete elimination of ionically charged species in the reaction
region surrounding the substrate is not always the desired goal. In
many instances, ionic species are required to reach the substrate
in order to perform the etch and/or deposition process. In these
instances, the ion suppressor may help to control the concentration
of ionic species in the reaction region at a level that assists the
process.
[0041] Showerhead 225 in combination with ion suppressor 223 may
allow a plasma present in chamber plasma region 215 to avoid
directly exciting gases in substrate processing region 233, while
still allowing excited species to travel from chamber plasma region
215 into substrate processing region 233. In this way, the chamber
may be configured to prevent the plasma from contacting a substrate
255 being etched. This may advantageously protect a variety of
intricate structures and films patterned on the substrate, which
may be damaged, dislocated, or otherwise warped if directly
contacted by a generated plasma. Additionally, when plasma is
allowed to contact the substrate or approach the substrate level,
the rate at which oxide species etch may increase. Accordingly, if
the exposed second material is oxide, this material may be further
protected by maintaining the plasma remotely from the
substrate.
[0042] The processing system may further include a power supply 240
electrically coupled with the processing chamber to provide
electric power to the faceplate 217, ion suppressor 223, showerhead
225, and/or pedestal 265 to generate a plasma in the first plasma
region 215 or processing region 233. The power supply may be
configured to deliver an adjustable amount of power to the chamber
depending on the process performed. Such a configuration may allow
for a tunable plasma to be used in the processes being performed.
Unlike a remote plasma unit, which is often presented with on or
off functionality, a tunable plasma may be configured to deliver a
specific amount of power to the plasma region 215. This in turn may
allow development of particular plasma characteristics such that
precursors may be dissociated in specific ways to enhance the
etching profiles produced by these precursors.
[0043] A plasma may be ignited either in chamber plasma region 215
above showerhead 225 or substrate processing region 233 below
showerhead 225. A plasma may be present in chamber plasma region
215 to produce the radical-fluorine precursors from an inflow of
the fluorine-containing precursor. An AC voltage typically in the
radio frequency (RF) range may be applied between the conductive
top portion of the processing chamber, such as faceplate 217, and
showerhead 225 and/or ion suppressor 223 to ignite a plasma in
chamber plasma region 215 during deposition. An RF power supply may
generate a high RF frequency of 13.56 MHz but may also generate
other frequencies alone or in combination with the 13.56 MHz
frequency.
[0044] Plasma power can be of a variety of frequencies or a
combination of multiple frequencies. In the exemplary processing
system the plasma may be provided by RF power delivered to
faceplate 217 relative to ion suppressor 223 and/or showerhead 225.
The RF power may be between about 10 watts and about 2000 watts,
between about 100 watts and about 2000 watts, between about 200
watts and about 1500 watts, or between about 200 watts and about
1000 watts in different embodiments. The RF frequency applied in
the exemplary processing system may be low RF frequencies less than
about 200 kHz, high RF frequencies between about 10 MHz and about
15 MHz, or microwave frequencies greater than or about 1 GHz in
different embodiments. The plasma power may be capacitively-coupled
(CCP) or inductively-coupled (ICP) into the remote plasma
region.
[0045] The top plasma region 215 may be left at low or no power
when a bottom plasma in the substrate processing region 233 is
turned on to, for example, cure a film or clean the interior
surfaces bordering substrate processing region 233. A plasma in
substrate processing region 233 may be ignited by applying an AC
voltage between showerhead 255 and the pedestal 265 or bottom of
the chamber. A cleaning gas may be introduced into substrate
processing region 233 while the plasma is present.
[0046] A fluid, such as a precursor, for example a
fluorine-containing precursor, may be flowed into the processing
region 233 by embodiments of the showerhead described herein.
Excited species derived from the process gas in the plasma region
215 may travel through apertures in the ion suppressor 223, and/or
showerhead 225 and react with an additional precursor flowing into
the processing region 233 from a separate portion of the
showerhead. Alternatively, if all precursor species are being
excited in plasma region 215, no additional precursors may be
flowed through the separate portion of the showerhead. Little or no
plasma may be present in the processing region 233. Excited
derivatives of the precursors may combine in the region above the
substrate and, on occasion, on the substrate to etch structures or
remove species on the substrate in disclosed applications.
[0047] Exciting the fluids in the first plasma region 215 directly,
or exciting the fluids in the RPS units 201, may provide several
benefits. The concentration of the excited species derived from the
fluids may be increased within the processing region 233 due to the
plasma in the first plasma region 215. This increase may result
from the location of the plasma in the first plasma region 215. The
processing region 233 may be located closer to the first plasma
region 215 than the remote plasma system (RPS) 201, leaving less
time for the excited species to leave excited states through
collisions with other gas molecules, walls of the chamber, and
surfaces of the showerhead.
[0048] The uniformity of the concentration of the excited species
derived from the process gas may also be increased within the
processing region 233. This may result from the shape of the first
plasma region 215, which may be more similar to the shape of the
processing region 233. Excited species created in the RPS 201 may
travel greater distances in order to pass through apertures near
the edges of the showerhead 225 relative to species that pass
through apertures near the center of the showerhead 225. The
greater distance may result in a reduced excitation of the excited
species and, for example, may result in a slower growth rate near
the edge of a substrate. Exciting the fluids in the first plasma
region 215 may mitigate this variation for the fluid flowed through
RPS 201, or alternatively bypassed around the RPS unit.
[0049] The processing gases may be excited in first plasma region
215 and may be passed through the showerhead 225 to the processing
region 233 in the excited state. While a plasma may be generated in
the processing region 233, a plasma may alternatively not be
generated in the processing region. In one example, the only
excitation of the processing gas or precursors may be from exciting
the processing gases in plasma region 215 to react with one another
in the processing region 233. As previously discussed, this may be
to protect the structures patterned on the substrate 255.
[0050] In addition to the fluid precursors, there may be other
gases introduced at varied times for varied purposes, including
carrier gases to aid delivery. A treatment gas may be introduced to
remove unwanted species from the chamber walls, the substrate, the
deposited film and/or the film during deposition. A treatment gas
may be excited in a plasma and then used to reduce or remove
residual content inside the chamber. In other disclosed embodiments
the treatment gas may be used without a plasma. When the treatment
gas includes water vapor, the delivery may be achieved using a mass
flow meter (MFM), an injection valve, or by commercially available
water vapor generators. The treatment gas may be introduced to the
processing region 233, either through the RPS unit or bypassing the
RPS unit, and may further be excited in the first plasma
region.
[0051] FIG. 2B shows a detailed view of the features affecting the
processing gas distribution through faceplate 217. As shown in
FIGS. 2A and 2B, faceplate 217, cooling plate 203, and gas inlet
assembly 205 intersect to define a gas supply region 258 into which
process gases may be delivered from gas inlet 205. The gases may
fill the gas supply region 258 and flow to first plasma region 215
through apertures 259 in faceplate 217. The apertures 259 may be
configured to direct flow in a substantially unidirectional manner
such that process gases may flow into processing region 233, but
may be partially or fully prevented from backflow into the gas
supply region 258 after traversing the faceplate 217.
[0052] The gas distribution assemblies such as showerhead 225 for
use in the processing chamber section 200 may be referred to as
dual channel showerheads (DCSH) and are additionally detailed in
the embodiments described in FIG. 2A as well as FIG. 2C herein. The
dual channel showerhead may provide for etching processes that
allow for separation of etchants outside of the processing region
233 to provide limited interaction with chamber components and each
other prior to being delivered into the processing region.
[0053] The showerhead 225 may comprise an upper plate 214 and a
lower plate 216. The plates may be coupled with one another to
define a volume 218 between the plates. The coupling of the plates
may be so as to provide first fluid channels 219 through the upper
and lower plates, and second fluid channels 221 through the lower
plate 216. The formed channels may be configured to provide fluid
access from the volume 218 through the lower plate 216 via second
fluid channels 221 alone, and the first fluid channels 219 may be
fluidly isolated from the volume 218 between the plates and the
second fluid channels 221. The volume 218 may be fluidly accessible
through a side of the gas distribution assembly 225. Although the
exemplary system of FIG. 2 includes a dual-channel showerhead, it
is understood that alternative distribution assemblies may be
utilized that maintain first and second precursors fluidly isolated
prior to the processing region 233. For example, a perforated plate
and tubes underneath the plate may be utilized, although other
configurations may operate with reduced efficiency or not provide
as uniform processing as the dual-channel showerhead as
described.
[0054] In the embodiment shown, showerhead 225 may distribute via
first fluid channels 219 process gases which contain plasma
effluents upon excitation by a plasma in chamber plasma region 215.
In embodiments, the process gas introduced into the RPS 201 and/or
chamber plasma region 215 may contain fluorine, e.g., CF.sub.4,
NF.sub.3 or XeF.sub.2. The process gas may also include a carrier
gas such as helium, argon, nitrogen (N.sub.2), etc. Plasma
effluents may include ionized or neutral derivatives of the process
gas and may also be referred to herein as a radical-fluorine
precursor referring to the atomic constituent of the process gas
introduced.
[0055] FIG. 2C is a bottom view of a showerhead 225 for use with a
processing chamber according to disclosed embodiments. Showerhead
225 corresponds with the showerhead shown in FIG. 2A. Through-holes
231, which show a view of first fluid channels 219, may have a
plurality of shapes and configurations in order to control and
affect the flow of precursors through the showerhead 225. Small
holes 227, which show a view of second fluid channels 221, may be
distributed substantially evenly over the surface of the
showerhead, even amongst the through-holes 231, which may help to
provide more even mixing of the precursors as they exit the
showerhead than other configurations.
[0056] An additional dual channel showerhead, as well as this
processing system and chamber, are more fully described in patent
application Ser. No. 13/251,714 filed on Oct. 3, 2011, which is
hereby incorporated by reference for all purposes to the extent not
inconsistent with the claimed features and description herein.
[0057] The chamber plasma region 215 or a region in an RPS may be
referred to as a remote plasma region. In embodiments, the radical
precursor, e.g., a radical-fluorine precursor, is created in the
remote plasma region and travels into the substrate processing
region where it may or may not combine with additional precursors.
In embodiments, the additional precursors are excited only by the
radical-fluorine precursor. Plasma power may essentially be applied
only to the remote plasma region in embodiments to ensure that the
radical-fluorine precursor provides the dominant excitation.
Nitrogen trifluoride or another fluorine-containing precursor may
be flowed into chamber plasma region 215 at rates between about 25
sccm and about 500 sccm, between about 50 sccm and about 150 sccm,
or between about 75 sccm and about 125 sccm in different
embodiments.
[0058] Combined flow rates of precursors into the chamber may
account for 0.05% to about 20% by volume of the overall gas
mixture; the remainder being carrier gases. The fluorine-containing
precursor may be flowed into the remote plasma region, but the
plasma effluents may have the same volumetric flow ratio in
embodiments. In the case of the fluorine-containing precursor, a
purge or carrier gas may be first initiated into the remote plasma
region before the fluorine-containing gas to stabilize the pressure
within the remote plasma region.
[0059] Substrate processing region 233 can be maintained at a
variety of pressures during the flow of precursors, any carrier
gases, and plasma effluents into substrate processing region 233.
The pressure may be maintained between about 0.1 mTorr and about
100 Torr, between about 1 Torr and about 20 Torr or between about 1
Torr and about 5 Torr in different embodiments.
[0060] Embodiments of the deposition systems may be incorporated
into larger fabrication systems for producing integrated circuit
chips. FIG. 3 shows one such system 300 of deposition, etching,
baking, and curing chambers according to disclosed embodiments. In
the figure, a pair of front opening unified pods (FOUPs) 302 supply
substrates of a variety of sizes that are received by robotic arms
304 and placed into a low pressure holding area 306 before being
placed into one of the substrate processing chambers 308a-f. A
second robotic arm 310 may be used to transport the substrate
wafers from the holding area 306 to the substrate processing
chambers 308a-f and back. Each substrate processing chamber 308a-f,
can be outfitted to perform a number of substrate processing
operations including the dry etch processes described herein in
addition to cyclical layer deposition (CLD), atomic layer
deposition (ALD), chemical vapor deposition (CVD), physical vapor
deposition (PVD), etch, pre-clean, degas, orientation, and other
substrate processes.
[0061] The substrate processing chambers 308a-f may include one or
more system components for depositing, annealing, curing and/or
etching a dielectric film on the substrate wafer. In one
configuration, two pairs of the processing chamber, e.g., 308c-d
and 308e-f, may be used to deposit dielectric material on the
substrate, and the third pair of processing chambers, e.g., 308a-b,
may be used to etch the deposited dielectric. In another
configuration, all three pairs of chambers, e.g., 308a-f, may be
configured to etch a dielectric film on the substrate. Any one or
more of the processes described may be carried out in chamber(s)
separated from the fabrication system shown in different
embodiments.
[0062] In the preceding description, for the purposes of
explanation, numerous details have been set forth in order to
provide an understanding of various embodiments of the present
invention. It will be apparent to one skilled in the art, however,
that certain embodiments may be practiced without some of these
details, or with additional details.
[0063] Having disclosed several embodiments, it will be recognized
by those of skill in the art that various modifications,
alternative constructions, and equivalents may be used without
departing from the spirit of the disclosed embodiments.
Additionally, a number of well-known processes and elements have
not been described in order to avoid unnecessarily obscuring the
present invention. Accordingly, the above description should not be
taken as limiting the scope of the invention.
[0064] Where a range of values is provided, it is understood that
each intervening value, to the smallest fraction of the unit of the
lower limit, unless the context clearly dictates otherwise, between
the upper and lower limits of that range is also specifically
disclosed. Each smaller range between any stated value or
intervening value in a stated range and any other stated or
intervening value in that stated range is encompassed. The upper
and lower limits of those smaller ranges may independently be
included or excluded in the range, and each range where either,
neither, or both limits are included in the smaller ranges is also
encompassed within the invention, subject to any specifically
excluded limit in the stated range. Where the stated range includes
one or both of the limits, ranges excluding either or both of those
included limits are also included.
[0065] As used herein and in the appended claims, the singular
forms "a", "an", and "the" include plural references unless the
context clearly dictates otherwise. Thus, for example, reference to
"an aperture" includes a plurality of such apertures, and reference
to "the plate" includes reference to one or more plates and
equivalents thereof known to those skilled in the art, and so
forth.
[0066] Also, the words "comprise(s)", "comprising", "contain(s)",
"containing", "include(s)", and "including", when used in this
specification and in the following claims, are intended to specify
the presence of stated features, integers, components, or steps,
but they do not preclude the presence or addition of one or more
other features, integers, components, steps, acts, or groups.
* * * * *